docs: def get_allcurrencycodes(self):
          """Return an iterable of distinct 3 character ISO 4217 currency codes"""
          foundcodes = []
          codeelements = self.currencies[0].iter('Ccy')
          for codeelement in codeelements:
              code = codeelement.text
              if code not in foundcodes:
                  foundcodes += [code]
                  yield code